Lattice and magnetic dynamics in perovskite Y1-xLaxTiO3

Inelastic neutron scattering combined with the dynamic pair density function (DPDF) analysis were used to investigate the magnetic and lattice dynamics in the orbitally active Y1-xLaxTiO3 as it crosses the antiferromagnetic (AFM) to ferromagnetic (FM) phase boundary. Upon doping, the FM state present in YTiO3 is suppressed on approaching a critical concentration of xc∼0.3 in which TC≃0, and is replaced by the AFM phase of LaTiO3. Below xc, magnetic scattering from spin waves is dominant at low energies. At xc with a TC≃0, magnetic scattering is also observed and is most likely due to AFM fluctuations. At the same time, local atomic fluctuations extending to 50 meV are observed above and below the magnetic transitions from 0≤x≤1 that show distinct characteristics with x. From Y to La, a clear difference is observed in the phonon density of states as a function of doping as well. At x=0.15 and 0.3, low-energy modes involving predominantly the rare-earth ion become suppressed with increasing temperature, while in x=1, strong suppression of phonon modes across a wide range in energy is observed above TN. It is likely that in the Y heavy samples, phonon modes below 20 meV have a stronger influence on the orbital excitations, while in LaTiO3, a strong phonon dependence is observed upon cooling up to TN.